The self-imposed lottery that cigarette smokers put themselves through each time they light up continues to astound me. Cigarette smokers are exposed to 5000-7000 chemicals, depending which cancer reference site you look at, but the experts all agree that this vast total includes about 70 carcinogens. Some of these will be recognisable to the general public, like formaldehyde, benzene and cyanide but there are plenty others that are highly dangerous, even though they aren’t so well-known.

The polycyclic aromatic hydrocarbons, generally referred to as PAHs, are well-represented in cigarette smoke, and one known as benzo[a]pyrene has been classified as a Group I carcinogen by the IARC. Its high toxicity and propensity to cause cancer has led to some research groups to have a look at BAP on its own.

During smoking, many compounds are initially trapped in the filter, which prevents their transfer into the air and protects other people to some extent. However, these chemicals can still move through the filter into the smoker’s mouth and the degree of exposure by this route has been examined by Chinese scientists in Rapid Communications in Mass Spectrometry.

They applied the technique of atmospheric pressure photoionisation linked to liquid chromatography/mass spectrometry to measure the levels of BAP in cigarette filters following smoking by 83 individuals. The mean levels were 8.36 ng/filter. A linear regression model for the BAP levels measured in mainstream smoke and the filters was established and used to estimate the exposures at mouth level as 20.79, 25.91 and 22.65 ng/cigarette for low, medium and high tar brands, respectively.

There was an excellent correlation between the oral exposure and the BAP levels in the filters, which presents an easy way forward for further investigation. Subjects involved in a smoking study simply smoke a cigarette in their natural surroundings and ship it to the lab. Subsequent analysis will lead to the BAP level in the filter, from which the oral exposure can be extrapolated.